DESCRIPTION: The product will be a packed capillary for nanoUHPLC of peptides that provides a dramatic increase in speed and efficiency. Current commercial columns for high speed and efficiency use sub-2 mm particles. The proposed technology uses sub-0.2 mm particles. The ability to use such small particles for UHPLC is enabled by the phenomenon of slip flow, which gives enhanced volume flow rates in reversed-phase liquid chromatography. Slip flow is a breakthrough that overcomes the fundamental limit to peak broadening caused by the parabolic velocity profile in the mobile phase. Using nonporous sub-0.2 mm particles also eliminates intraparticle diffusion while giving high phase ratios. Preliminary results show that sub micrometer nonporous silica particles reach the diffusion limit for efficiency in protein separations, and the diffusion limit is expected to be reached for the faster diffusing peptides. This gives plate numbers that are independent of length, allowing columns less than 2 cm in length to give 100,000 plates with high speed. The specific aims are to 1) optimize the particle diameter, 2) optimize the separation length, and 3) evaluate the nano LC-MS of a tryptic digest.